The invention relates to a device for collecting a soft biological sample and to a method of using said device.
Biological assays using reagents with a mutual affinity have been known for decades. They involve a biological sample suspected of containing an analyte and one or more reagents with an affinity or ability to react with the analyte in the sample.
The test sample is most frequently a patient""s or individual""s body fluid such as a sample of whole blood, plasma, serum, urine, cerebrospinal fluid, etc. A sample of biological fluid can be collected simply by using any appropriate device such as a pipette, a syringe, an automatic sample collector, etc. In some cases it may need to be filtered beforehand in order to remove all kinds of unwanted debris or microorganisms. In general terms the methods of sampling body fluids which are performed on a day-to-day basis are satisfactory: they are generally reproducible, giving quantitative results, and the devices available on the market are reliable and relatively inexpensive.
The sample can also consist of a biological solid, such as an organ or tissue fragment, which is not distributed in a systematically homogeneous manner in the sampling device. In this case the method of collecting the sample is much more complex and the devices often have to be adapted to each particular case according to the greater or lesser fluidity or viscosity of these body solids.
A very large number of common analyses and screenings are currently performed on fluid samples. This is not the case of the tests currently performed in the diagnosis of transmissible spongiform encephalopathies (TSE), which are degenerative neurological diseases such as scrapie in sheep, xe2x80x9cmad cow diseasexe2x80x9d, also called bovine spongiform encephalopathy (hereafter xe2x80x9cBSExe2x80x9d), in cattle, Creutzfeldt-Jakob disease (CJD) and kuru in humans, and related transmissible spongiform encephalopathies.
In the case of BSE, there is not yet a common in vitro diagnostic test which can be performed on a sample of body fluid, but only a test which can be performed on brain samples collected after the animal has been slaughtered. The postmortem examination reveals vacuolations in the cells of the bovine brain tissue and deposits of a specific marker of this disease, namely PrPres (abnormal form of a protein called xe2x80x9cprion proteinxe2x80x9d). Diagnosis currently requires a sample to be collected from the brain matter, especially from the animal""s brain stem and more particularly from the sensory and motor nuclei of the vagus nerve, which constitute the zone of preferential accumulation of PrPres, the diagnostic marker of BSE.
The sample collected is then subjected to various treatments for extraction of the PrPres, the specific marker of the disease, which is then analyzed by immunoassay.
The recent incidence of BSE in Great Britain (since 1985), and subsequently in Europe, is the cause of a very considerable public health problem in view of the possibility of transmission of the disease to humans, and its eradication has consequently become of very great economic importance.
In view of its plastic properties and its viscosity, bovine brain matter is not easy to sample in a simple, rapid, reproducible, quantifiable and safe manner. Now, for a mass screening of bovine carcasses, it is essential that the testsxe2x80x94and hence the samplingxe2x80x94are effected in the simplest manner usable in an abattoir, as quickly as possible after slaughter and as reproducibly, quantifiably and safely as possible, i.e. with the best possible sensitivity and without external contamination.
Conventionally, when a sample of brain matter is collected for analysis for the presence of PrPres, it is necessary to use an elaborate protocol which involves cutting off the head, possibly opening the brainpan, seizing a piece of brain matter, for example with a spoon, curette or any appropriate instrument of this kind, and manually cutting off, with a scalpel, at least one portion of said matter until the necessary weight is obtained, which must then be checked with a balance. The scalpel blade has to be changed for each sampling so as to avoid any contamination between samples. This protocol therefore proves rather inconvenient in practice and rather inappropriate for mass screening.
Finally, the sampling operation must be as inexpensive as possible (in terms of equipment and labor) for the final consumer, for obvious reasons.
There is therefore an urgent need for a device for collecting a soft biological sample, particularly brain matter, which is simple, can be used for example in an abattoir or in an analytical laboratory, is quick to use, is economic, has a reproducible performance and is quantifiable, effective and safe from any external contamination. There is also an urgent need for a method of carrying out this type of sampling. The object of the present invention was to meet these needs.
In general, such a need still exists in all situations where it is necessary to collect a soft biological sample, and not only in the area of spongiform disease in cattle or scrapie in sheep.
The inventors have now found that it is possible to collect a reproducible volume of a soft biological sample using a device equipped with a slicing end, making it possible to effect a clean section of the soft matter constituting a sample. In particular, the inventors have discovered that it is possible to collect a constant mass of soft matter using a hollow cylindrical device equipped at one end with a slicing section carrying one or more cutting wires, positioned diametrically and perpendicularly to the axis of said hollow cylindrical body, when said cylindrical device is rotated to a sufficient extent about itself.
xe2x80x9cSoft biological samplexe2x80x9d is to be understood as meaning a sample of a biological material whose consistency is such that it can be cut effortlessly with a tool such as a scalpel. As indicated previously, an example of such a biological material is brain matter.
xe2x80x9cBrain matterxe2x80x9d is to be understood as meaning any portion of the mass constituting the central nervous system, and particularly, but not exclusively, the anatomical part conventionally called the xe2x80x9cbrain stemxe2x80x9d, especially that which is centered on the sensory and motor nuclei of the vagus nerve, whether said matter be in the natural state or whether it has been treated, e.g. obtained in the form of a pasty ground material.
The invention therefore relates to a device for collecting a soft biological sample, especially of brain matter, comprising a hollow cylindrical body with two openings, one at each end, wherein a piston with a rod is inserted via a first end and said piston-and-rod assembly can be displaced back and forth inside said hollow cylindrical body, characterized in that the opening in the second end of the hollow cylindrical body has a slicing edge and in that said second end carries at least one cutting wire arranged across this opening.
The edge of the second end of the hollow cylindrical body slices sufficiently well to penetrate the soft biological sample by cutting it. The sharpness of the edge may be chosen according to the nature of the sample.
The hollow cylindrical body is advantageously transparent and the piston is advantageously opaque and colored. The hollow cylindrical body and the piston have to be chosen so as to allow and assure substantial leaktightness between them.
The device advantageously has means of identifying a volume corresponding to a variation in the position of the piston in the body. These means comprise e.g. one or more visible marks located in one or more different positions on the hollow cylindrical body and delimiting one or more given cylindrical volumes. Preferably, but not exclusively, the number of visible marks according to the invention is at least two.
The xe2x80x9cvisible marksxe2x80x9d according to the invention, also called identification means, can consist e.g. of conventional graduations, such as those shown in FIG. 1, or of a variety of geometric symbols such as squares, circles, triangles or any symbol of this kind, arranged according to a xe2x80x9cpitchxe2x80x9d to enable the desired volume to be selected. The word xe2x80x9cpitchxe2x80x9d is understood here as meaning the distance between two identical marks, for example, but not exclusively, the distance between two identical geometric symbols, namely two triangles, two squares or two circles.
As a variant, the visible marks (at least two) can be located on the rod in at least two different positions in order to define a given cylindrical volume when the rod is displaced by one pitch, i.e. from a first position, in which the first mark coincides with a given zone of the hollow cylindrical body, to a second position, in which the second mark coincides with said zone of the hollow cylindrical body.
Advantageously, the slicing edge of the second end of the hollow cylindrical body is formed by a gradual reduction in the thickness of the wall of this body to give the end a frustoconical shape, or by a chamfer at the end of said body.
Advantageously, the cutting wire is arranged diametrically across the opening in the second end of the hollow cylindrical body and is oriented perpendicularly to the axis of said body.
The steps involved in collecting a soft biological sample using a device according to the invention are as follows:
(1) said device is applied to the surface of said sample, the second end of the hollow cylindrical body being in direct contact with said sample, and the piston-and-rod assembly is then pushed as far as it will go in the forward direction, i.e. towards said second end,
(2) said hollow cylindrical body is pushed into said sample to the desired depth while the piston is kept at the surface of said sample,
(3) when said hollow cylindrical body has reached the desired depth of penetration, said hollow cylindrical body is rotated about its axis to cut the sample by means of at least one cutting wire, and
(4) said hollow cylindrical body and said piston-and-rod assembly, kept as such, are withdrawn from the sample together.
The sample collected may subsequently be extruded from the body of the device, cut and released in order to be dispensed into an appropriate container for detection and/or quantification of the analyte contained in the sample. The sample extrusion and release operations will be described in detail below.
Advantageously, the rotation which enables the wire to cut the sample is performed over 360 degrees.
If the device has the identification means referred to above, these are utilized to identify a sampling volume corresponding to a given penetration of the hollow cylindrical body into the sample and/or to identify a volume extruded from the body of the device for the purpose of analysis.
Thus, if these identification means comprise two visible marks arranged on the hollow cylindrical body, the latter can be pushed into the sample up to a position corresponding to a sampling volume at least equal to the volume given by the mark furthest from the second end of the hollow cylindrical body. An amount given by the displacement of the piston towards the second end of the hollow cylindrical body, between the two marks, can then be kept as the volume for analysis.
If the two visible marks are arranged on the piston rod, the hollow cylindrical body can be pushed into the sample up to a position corresponding to a sampling volume at least equal to the volume given by the mark closest to the end of the rod which carries the piston. An amount given by the displacement of the piston towards the second end of the hollow cylindrical body, between two positions in which this mark and then the other mark successively coincide with a given zone of the hollow cylindrical body, can then be kept as the volume for analysis.
The invention also includes all the variants or combinations which are obvious to those skilled in the art without departing from the spirit of the present invention, for the widest variety of applications in which it is necessary to collect a portion of a soft biological sample.